(1) Field of the Invention
The present invention pertains to a self-locking wiring grommet that is attachable to an opening in a housing of an electrical device. The grommet protects the electrical wiring of the device passed through the housing opening from being scraped or cut by the edge of the opening, and seals the housing opening against dirt, dust, moisture or other matter that could detrimentally affect the operation of the electrical device. In particular, the present invention pertains to a self-locking wiring grommet that is inserted into a notch at an edge of a clamshell housing of an electrical device to protect the wiring of the device, where the grommet has a pair of resilient arms that flex toward each other as the grommet is inserted into the notch and then spring outwardly away from each other to engage with a perimeter flange at the edge of the housing to hold the grommet in the housing notch without the need for separate fasteners.
(2) Description of the Related Art
Electrical devices, for example electric motors, are often contained in metal housings that provide a supporting base for the device and protect the component parts of the device. The housing of the electrical device is provided with an opening and the wiring of the electrical device is passed through the opening to the exterior of the housing. To protect the insulation of the electrical wiring of the device, a grommet is usually attached to the edge portions of the housing surrounding the housing opening. In this way the grommet protects the wiring insulation from being scraped or cut by the metal edge of the housing opening.
Because the attachment of the grommet to the electrical device housing requires additional manufacturing steps that increase the cost of manufacturing the device, different types of housings and grommets have been designed whereby the grommet can be easily attached to the device housing without the need for separate fasteners. One example is employed on the cylindrical shell housing of an electric motor that is used with a pair of end shields that are secured in the openings at the opposite ends of the cylindrical shell and support bearings of the motor shaft. A notch is formed in one of the ends of the cylindrical shell and a grommet, through which the wiring of the motor is passed, is inserted into the notch. One of the end shields is attached to the end of the cylindrical shell over the notch. This end shield holds the grommet in the notch without the need for separate fasteners securing the grommet to the notch.
Although this design of motor housing enables the wiring grommet to be attached to the housing without the need for separate fasteners and without the additional manufacturing step of attaching the grommet by fasteners, it also has disadvantages. For example, when the wiring grommet is inserted into the notch it must be held in the notch until the end shield is attached to the cylindrical housing shell to secure the grommet in the notch. During manufacture of the motor, it is possible for the grommet to fall out of the notch, requiring its reinsertion and increasing the manufacturing time for the motor and its associated costs.
The wiring grommet of the present invention overcomes the disadvantages associated with prior art wiring grommets by providing a self-locking feature on a wiring grommet that holds the grommet in a notch of an electrical device housing. The self-locking wiring grommet of the invention is designed for use with a clamshell motor housing. Clamshell motor housings typically have two housing sections that are substantially the same. Each housing section has a generally cup-shaped configuration with a cylindrical side wall and a circular end wall. A motor shaft opening is provided at the center of the end wall. The side wall has a peripheral edge that is formed as a radially out-turned flange. The flanges of the two clamshell housing sections are secured together by rivets or other equivalent means, with the motor or other electrical device enclosed in the interior of the two clamshell housing sections.
To accommodate the wiring grommet of the invention, a notch is formed into a side wall of one of the clamshell housing sections. The notch forms an opening in the housing section side wall that is dimensioned to receive the grommet. The notch also forms a gap in the peripheral flange of the housing section adjacent the notch. The opposite housing section is not provided with a notch.
The self-locking wiring grommet of the invention is basically comprised of a base dimensioned to be inserted into the housing section notch, a tubular portion projecting from the base and designed to be attached to a wiring conduit, a center bore through the base and tubular portion, and in the preferred embodiment, a pair of resilient arms that project outwardly from the grommet. The base has a peripheral surface that is shaped complementary to the configuration of the notch formed in the housing section. A slot is recessed into a portion of the peripheral surface and is dimensioned to receive a portion of the motor housing side wall surrounding the notch. The base of the grommet is inserted into the notch with an interior surface of the base facing the interior volume of the housing section, an exterior surface of the base facing away from the housing side wall, the tubular portion of the grommet projecting outwardly from the base exterior surface, and with a sealing portion of the base peripheral surface spanning across the gap in the housing section peripheral flange created by the notch. As the grommet base is inserted into the notch, the resilient arms pass through the gap in the housing peripheral flange and resiliently flexed toward each other. As the distal ends of the arms pass through the gap, the resiliency of the arms causes them to flex outwardly away from each other and engage against the housing section peripheral flange on opposite sides of the gap, thereby securely holding the grommet in the notch without the need for separate fasteners and without the need for the other housing section being attached to the housing section with the notch. With the resilient arms holding the grommet in the housing section notch, the wiring of the electrical device can be passed through the bore of the grommet. The other housing section can then be attached to the housing section with the notch without the risk of the grommet separating from the notch prior to the attachment of the other housing section.